This invention relates generally to event data collection and more particularly to vehicle traffic counting and recording.
In the past, traffic volume counting has been performed by multiple channel field recorders which punched a binary code and/or printed the recorded volumes onto a paper tape. The paper tape media was then transported into the office for review and analysis. The paper tape recorders and media had many problems. They required many hours of time to transfer data into a usable format. For those who could afford an electronic reader, however, the time commitment was substantially reduced. Nevertheless, the reader was not without problems. The mechanisms would get dirty and erroneous information would be translated to the output, and if the punch of the original tape was not clean, and incorrect data would be transferred. Another problem was that software was not readily available to process data and produce needed results.
Solid state technology has created an environment that permits data to be stored electronically, thus reducing the need for human and mechanical interface. Solid state technology has also improved the accuracy of vehicular counting. Various forms of solid state equipment have been developed for use in traffic control and, more generally, for event data acquisition.
U.S. Pat. Nos. 3,397,305 and 3,397,306 to Auer, Jr. disclose solid state traffic volume measuring devices for counting vehicles passing a vehicle presence detector over periodic intervals of time, storing the count, or an average thereof, for each interval and resetting the counter. The count or average count is provided to a utilization device, which can be an indicator, a traffic signal control system, or a computer. U.S. Pat. No. 3,549,869 to Kuhn discloses a modular counting system that can be plugged into, or unplugged, from a traffic detecting system. U.S. Pat. No. 3,711,386 to Apitz similarly shows a traffic volume that provides traffic volume as percentage of a standard or reference unit volume. U.S. Pat. No. 4,258,430 to Tyburski also discloses a traffic counter, with a detachable, battery-powered random access memory unit so that stored count data can be transported from the field to an office-located computer for unloading data for further processing.
These systems all implement their particular functions in hardware electronics circuitry, although Tyburski mentions that a microprocessor could be used to perform the traffic detection and counting functions. It is also known to use a microprocessor in other, similar traffic control applications. For example, the Multisonics, Inc. 901 Controller is a microcomputer designed to control traffic signals based on traffic volume in each lane of traffic at an intersection. A typical quad intersection with a traffic lane and a turn lane in each direction has eight phases. The 901 Controller has a microprocessor, a program ROM, an addressable RAM, a clock, external inputs from traffic transducers and outputs for controlling operation of a traffic signal. The traffic volume computation, storage and signal control functions for each phase are implemented and coordinated in software. Thus, they can be changed more readily than in the foregoing hardware implementations. The 901 Controller, however, is designed for use at fixed locations, rather than at many, varied locations.
Other portable event tabulation and counting devices are known. U.S. Pat. No. 3,878,371 to Burke discloses an apparatus and method for compiling and recording data on the operation of vehicles, such as the number of times that the vehicle is started. U.S. Pat. No. 3,922,649 to Thome and U.S. Pat. No. 3,959,633 to Lawrence disclose electronic watchman's tour recording devices. Data is recorded in the portable unit and then the unit is returned to an office-located computer to unload the data for further processing.
All of the foregoing designs have several drawbacks. One drawback is that their adoption typically requires the user to discard all prior equipment and replace it with an entirely new system. This entails considerable capital expense. As a result, in the connection with traffic counting, many traffic departments cannot afford the costs of changeover. Consequently, many are still using the obsolete paper punch systems. Another drawback is that prior traffic volume data acquisition systems require initialization. The procedure can be rather complex, beyond the ordinary skills of traffic field workmen. Besides setting the machine to operate as desired, the workmen must correctly log various kinds of information, and this information must be correctly input to the office-located computer for correlation with the recorded data. As a result, mistakes in setting the traffic counters and logging information can be and frequently are made, sometimes causing many valuable days of data to be lost or improperly recorded or processed. Another drawback is that many of these designs, particularly those disclosed in Tyburski, Lawrence, Thome and Burke, require that the data module be taken into the office and plugged into an expensive reader or interface unit for inputting the data to a computer.
Accordingly, a better, more economical system is needed for recording traffic volume and other forms of event data.